tracing: Add enabling of events to boot instances

Add the format of:

  trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall

That will create the "foo" instance and enable the sched_switch event
(here were the "sched" system is explicitly specified), the
irq_handler_entry event, and all events under the system initcall.

Link: https://lkml.kernel.org/r/20230207173026.386114535@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ross Zwisler <zwisler@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9545da5..40304dc 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6278,6 +6278,20 @@
 
                                /sys/kernel/tracing/instances
 
+                       Events can be enabled at the time the instance is created
+                       via:
+
+                               trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
+
+                       Note, the "<system*>:" portion is optional if the event is
+                       unique.
+
+                               trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
+
+                       will enable the "sched_switch" event (note, the "sched:" is optional, and
+                       the same thing would happen if it was left off). The irq_handler_entry
+                       event, and all events under the "initcall" system.
+
        trace_options=[option-list]
                        [FTRACE] Enable or disable tracer options at boot.
                        The option-list is a comma delimited list of options

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 863716f..5b16af9 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -10188,6 +10188,10 @@ __init static void enable_instances(void)
                }
                /* Allow user space to delete it */
                trace_array_put(tr);
+
+               while ((tok = strsep(&curr_str, ","))) {
+                       early_enable_events(tr, tok, true);
+               }
        }
 }
 

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index d16929d..f10bf80 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1334,6 +1334,8 @@ DECLARE_PER_CPU(int, trace_buffered_event_cnt);
 void trace_buffered_event_disable(void);
 void trace_buffered_event_enable(void);
 
+void early_enable_events(struct trace_array *tr, char *buf, bool disable_first);
+
 static inline void
 __trace_event_discard_commit(struct trace_buffer *buffer,
                             struct ring_buffer_event *event)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index b07931a..cf3fd74 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3750,10 +3750,9 @@ static __init int event_trace_memsetup(void)
        return 0;
 }
 
-static __init void
-early_enable_events(struct trace_array *tr, bool disable_first)
+__init void
+early_enable_events(struct trace_array *tr, char *buf, bool disable_first)
 {
-       char *buf = bootup_event_buf;
        char *token;
        int ret;
 
@@ -3806,7 +3805,7 @@ static __init int event_trace_enable(void)
         */
        __trace_early_add_events(tr);
 
-       early_enable_events(tr, false);
+       early_enable_events(tr, bootup_event_buf, false);
 
        trace_printk_start_comm();
 
@@ -3834,7 +3833,7 @@ static __init int event_trace_enable_again(void)
        if (!tr)
                return -ENODEV;
 
-       early_enable_events(tr, true);
+       early_enable_events(tr, bootup_event_buf, true);
 
        return 0;
 }